Providing annotations of a digital work

ABSTRACT

A digital work may be annotated using an eBook reader device. Upon receiving an annotation relating to a specific portion of the digital work, an invariant location reference identifier corresponding to the specified portion of the digital work may be appended to the annotation. The annotation may then be stored in association with the digital work for later reference. In some instances, an annotation may be presented on an eBook reader device upon receipt of a valid authorization credential granting access to the annotation.

RELATED APPLICATIONS

This application is a continuation-in-part of copending U.S. patentapplication Ser. No. 11/039,645, filed Jan. 19, 2005, and entitled“Method and System for Providing Annotations of a Digital Work” andclaims the benefit of U.S. Provisional Application No. 60/882,870, filedDec. 29, 2006, and entitled “Invariant Referencing in Digital Works,”both of which are incorporated herein by reference.

BACKGROUND OF THE INVENTION

For many years, print media provided the only way to transmitinformation and ideas in a fixed form. With the advent of photographyand audio recording, additional media have become available fortransmitting information and ideas. Moreover, with the widespread use ofthe Internet, it has become possible to distribute large, coherent unitsof media, such as books, using electronic technologies. The informationin such media, however, is static. That is, updated information isprovided only by preparing and distributing additional media. However,widespread distribution of updated information, including comments,supplements, features, thoughts, insights, etc., becomes difficult whenthe information is authored by multiple parties. Media consumers havingadditional information or insight typically do not have a way toeffectively share that information with other consumers. What is neededis a method and system that allows users of media to easily annotate themedia and afterward distribute such annotations to others in aneconomical and efficient manner.

Another problem that arises with electronic media is that displayconditions (e.g., screen size, font type or size, screen resolution,margins, line spacing, etc.) affect the amount of content that can bedisplayed on a given display screen. Electronic media is typicallystructured as virtual frames presented on a display device, and a usermay turn or change from one virtual frame or “page” of electroniccontent to another. The term “page” as used herein refers to acollection of content that is presented at one time on a display. Thus,“pages” as described herein are not fixed permanently, and may beredefined or repaginated based on variances in display conditions, suchas screen size, font type or size, margins, line spacing, resolution, orthe like. Accordingly, it may be difficult or impossible for a userreading electronic media on one display device to meaningfullycommunicate a page cite or annotation to a reader of the same electronicmedia on another display device, because one or more of the foregoingdisplay conditions may be different.

BRIEF SUMMARY

In view of the above, this disclosure describes exemplary ways ofannotating a digital work, conveying locations of annotations within adigital work, providing access to annotations, as well as otherexemplary aspects. In one aspect, a digital work may be annotated atleast partially using an eBook reader device. The eBook reader devicereceives an annotation. If the annotation relates to a specific portionof the digital work, an invariant location reference identifiercorresponding to the specified portion of the digital work may beappended to the annotation. The annotation may then be stored inassociation with the digital work.

In another aspect, an annotation of a digital work may be presented onan eBook reader device. The annotation is received at the eBook readerdevice. The received annotation may then be stored in association withthe digital work. The eBook reader device may also receive anauthorization credential granting access to the annotation and, if theauthorization credential is valid, may present the annotation of thedigital work on the eBook reader device in context with regard to thedigital work.

In yet another aspect, an eBook reader device includes a processor andmemory in communication with the processor. One or more digital worksare stored in the memory, along with one or more annotations associatedwith the digital works. The annotations are separate from the digitalworks, such that the digital works are unaltered by the provision of theannotations.

BRIEF DESCRIPTION OF THE DRAWINGS

The detailed description is set forth with reference to the accompanyingfigures. In the figures, the left-most digit(s) of a reference numberidentifies the figure in which the reference number first appears. Theuse of the same reference numbers in different figures indicates similaror identical items.

FIG. 1 is a pictorial diagram of an exemplary computing environment thatincludes a server system and a number of client systems communicativelyconnected via a network;

FIG. 2 is a schematic block diagram of an exemplary implementation of aserver system that may be used in the computing environment of FIG. 1;

FIG. 3 is a pictorial diagram of an exemplary client system that may beused with the computing environment of FIG. 1;

FIG. 4 is a pictorial diagram illustrating an implementation in whichtwo client devices are displaying content of a digital work, along witha conventional page number on which the displayed content appears;

FIG. 5 is a pictorial diagram illustrating an implementation in whichtwo exemplary client devices are displaying content of the same digitalwork, along with a location reference identifier identifying a locationin the digital work at which the displayed content appears;

FIG. 6 is a flow diagram of an exemplary method o for receipt anddistribution of annotations;

FIG. 7 is a flow diagram of an exemplary method of annotating a digitalwork;

FIG. 8 is a flow diagram illustrating an exemplary payment and feedbackaspect;

FIG. 9 is a pictorial diagram of an exemplary Web page formed inaccordance with an implementation, presenting a digital work andannotations in textual format;

FIG. 10 is a pictorial diagram of an exemplary Web page formed inaccordance with another implementation, presenting textual annotationsin a separate window;

FIG. 11 is a pictorial diagram of an exemplary Web page formed inaccordance with yet another implementation, presenting graphicalhandwritten annotations superposed on a textual digital work;

FIG. 12 is a pictorial diagram of an exemplary Web page formed inaccordance with still another implementation, presenting a digital workand/or annotations in an audio or audiovisual format; and

FIG. 13 is a pictorial diagram of an exemplary Web page formed inaccordance with another implementation, presenting a digital work andannotations in a textual format, with the annotations presented to auser in a list.

DETAILED DESCRIPTION

Overview

This disclosure describes annotation of digital works and presentingannotations of digital works. In particular, in some implementations,annotations may be created and/or presented on an eBook reader device orother suitable display device. The amount of content that can bedisplayed on a given display of the eBook reader or other display devicemay be affected by various display conditions, such as screen size, fonttype or size, screen resolution, margins, line spacing, etc. Thisproblem arises because the virtual frames or “pages” displayed on thedisplay device are not fixed permanently, and may be redefined orrepaginated based on variances in the display conditions. Accordingly,it may be difficult or impossible for a user reading a digital work onone display device to meaningfully communicate a page cite to a readerof the same digital work on another display device, because one or moreof the foregoing display conditions may be different. Consequently,annotations of a digital work that are based on a “page” citation to thedigital work may not accurately communicate the portion of the digitalwork to which the annotation applies. Moreover, the annotation may notbe displayed in the intended location if the display conditions aredifferent than when the annotation was authored.

Invariant referencing of locations within a digital work allows a userto accurately reference a location within a digital work, regardless ofscreen size, font type, font size, or other variations in displayconditions of the digital work. Briefly, invariant referencing oflocations is accomplished by assigning unique reference identifiers atlocations throughout the content of a digital work, or to individualsegments of the digital work. These reference identifiers are notdependent on display conditions of a display device on which the digitalwork is displayed. In that sense, the reference characters areinvariant. The invariant location reference identifiers provide areliable means by which a user can determine a location of content inthe digital work and approximately where the content is relative to thebeginning and end of the digital work. Invariant location referenceidentifiers may also be used as a means of identifying a location, orsection of content, within a digital work with which an annotation isassociated.

Also, once an annotation of a digital work has been authored, it may bedesirable to share the annotation with other users. The annotation maybe shared with other users in a variety of ways, including transmissionto another display device directly (e.g., peer-to-peer) or via one ormore remote servers and/or databases. The annotations may be transmittedvia wired and/or wireless connection, and may be transmitted togetherwith, or separately from, the digital work to which the annotationapplies. Depending on the circumstances, it may be desirable to limitdistribution of the annotation. Accordingly, in some implementations, anauthorization credential may be required in order to access theannotation.

Exemplary Computing Environment

FIG. 1 provides an exemplary overview of one computing environment inwhich implementations of the invention may be implemented. The depictedenvironment includes a server system 102 and one or more client systems104, 106 communicatively connected by a network 108. The client system104 is shown associated with a user 120, and the client system 106 isshown associated with a user 122. Also depicted in FIG. 1 are clientsystems 130, 132 communicatively connected to the server system 102 viathe network 108. The client system 130 is shown associated with anauthor 134, and the client system 132 is shown associated with an author136. The client devices 104, 106, 130, and 132 may additionally oralternatively be communicable with one another via peer-to-peer wired orwireless connections, as shown by the arrow between client devices 106and 132.

In FIG. 1, client systems 104 and 130 are illustrated as personalcomputers (PCs) and client systems 106 and 132 are illustrated asspecialized eBook reader devices. However, the concepts described hereinare applicable to any number or combination of additional or alternativeclient devices including, for example, portable computers (e.g., laptopsor pocket PCs), personal digital assistants (PDAs), portable gamingdevices, wireless phones, and the like.

The terms “user”, “author” and “source” are generally used herein. A“user” typically refers to a person, entity or device that seeks toreceive an annotation previously stored in association with a digitalwork. An “author” typically refers to a person, entity or device thatprepares an annotation for storage and distribution to users. A “source”typically refers to a person, entity, or device that originates adigital work that may be annotated by an “author”. As should be readilyappreciated, a person, entity or device can be a source, an authorand/or a user, depending on the distribution of a digital work andwhether an annotation is being prepared or requested. Accordingly, atdifferent times, the users 120, 122 can be “authors” and the authors134, 136 can be “users”, and any of them (or some other third party) maybe the source of a digital work.

As will be described with regard to the particular implementations shownherein, the server system 102 is configured to exchange data andinformation, including digital works and annotations thereof, with theusers 120, 122 who are operating the client systems 104, 106 and theauthors 134, 136 who are operating the client systems 130, 132. In somecircumstances, the server system 102 may be associated with a merchant,such as an online retailer authorized to provide a marketplace forselling and distributing digital works to consumers. Exemplaryimplementations are described herein in the context of electronic books(“eBooks”) or “digital works.” The terms “eBook” and “digital work” areused synonymously and, as used herein, may include any type of contentthat can be stored and distributed in digital form. By way ofillustration, without limitation, digital works and eBooks can includeall forms of textual information such as books, magazines, newspapers,newsletters, periodicals, journals, reference materials, telephonebooks, textbooks, anthologies, proceedings of meetings, forms,directories, maps, manuals, guides, references, photographs, articles,reports, documents, etc., and all forms of audio and audiovisual workssuch as music, multimedia presentations, audio books, movies, etc.

Digital works may be stored as media files in a digital works database124 that resides in or is otherwise communicatively connected to theserver system 102. An annotations database 126 and a transactioninformation database 128 are also shown in FIG. 1 residing in orotherwise communicatively connected to the server system 102 and will bedescribed in greater detail below. The server system 102, separately ortogether with the databases 124, 126, and 128, may provide an onlinemarketplace 138 that can receive and distribute annotations as well asthe digital works to which the annotations pertain.

The network 108 shown in FIG. 1 may be a local area network (LAN) or alarger network, such as a wide area network (WAN), collection ofnetworks, or the Internet. Protocols for network communication, such asTCP/IP, are well known to those skilled in the art of computer networks.An author, such as author 134, may operate a client system, such asclient system 130, to request a digital work from the server system 102via the network 108. The author 134 operating the client system 130 mayalso provide 136 annotations of a digital work to the server system 102for storage in the annotations database 126 and the server system 102may provide 138 the annotations of the digital work to others, such asthe user 122 of the device 106 receiving 140 the annotations of thedigital work from the server system 102 via the network 108. The user122 may operate the client system 106 to request digital works and/orannotations thereof from the server system 102. As will be appreciatedby those skilled in the art and others, FIG. 1 provides a simplifiedexample of one suitable computing environment for implementingimplementations of the present invention, and the invention is notlimited thereto.

When software formed in accordance with the invention is implemented inone or more computer systems, for example, of the type illustrated inFIG. 1, the computer systems provide a way for authors and users toaccess digital works, provide annotations thereto, and receiveannotations of digital works. Providing a mechanism for annotation of adigital work and providing a mechanism for distribution of theannotation makes the underlying digital work more useful and valuable byproviding improved or clarifying material in the digital work, updatingmaterial, correcting material, adding academic interest or “color” tothe material, providing editorial comments to the material, etc.Implementations of the invention may be implemented such that authors ofannotations may receive some or all of compensation paid by other usersto access the annotations.

Exemplary Server System

FIG. 2 depicts an exemplary computer architecture for a server system,such as the server system 102, that may be used to implementimplementations of the invention discussed herein. Of course, personsskilled in computers will appreciate that other server systems suitablefor use may include more or fewer components than those shown in FIG. 2.

The server system 102 shown in FIG. 2 is connected to the network 108(FIG. 1) using a network interface 200. The network interface 200includes hardware and software that allows the server system 102 tocommunicate with other computing devices connected to the network 108 byuse of one or more suitable communication protocols, such as TCP/IP.

The server system 102 shown in FIG. 2 further includes a processor 202,a memory 204, a video display adapter 206, a disk drive 208, and aninput/output interface 210, all of which are communicatively connectedtogether and to the network interface 200 by a communication bus 212.The memory 204 generally comprises RAM, ROM, and/or other volatile orpermanent memory. The memory 204 is shown storing an operating system214 for controlling the operation of the server system 102. A binaryinput/output system (BIOS) 216 for controlling the low-level operationof the server system 102 is also stored in the memory 204.

The memory 204 additionally stores program code and data for providingnetwork services that allow client systems to exchange information anddata files with the server system 102. Accordingly, the memory 204 maystore a Web server application 218, which may be provided by any one ofa number of commercially available software packages. The Web serverapplication 218 comprises computer executable instructions, that, whenexecuted by the processor 202, generate or otherwise obtain configurablemarkup documents such as the sample Web pages shown in FIGS. 9-13, fordisplay on client systems. The Web server application 218 communicateswith a database manager application 220 and a transaction managerapplication 222 that facilitate additional functions of the serversystem 102 described below.

The video display adapter 206 provides display signals to a localdisplay (not shown in FIG. 2) permitting an operator of the serversystem 102 to monitor and configure the operation of the server system.The input/output interface 210 likewise communicates with externaldevices not shown in FIG. 2, such as a mouse, keyboard, scanner, orother input and output devices that can be operated by an operator ofthe server system 102.

Further included in the server system 102 is a mass storage 224comprising facilities such as one or more CD-RW/DVD-RW drives, hard diskdrives, tape drives, etc., or combinations thereof, that are utilized tostore digital content and information, such as annotations. In theimplementation shown in FIGS. 1 and 2, the mass storage 224 contains thedigital works database 124, annotations database 126, and transactioninformation database 128.

Turning back to FIG. 1, the client systems 104, 106, 130, and 132 maytake the form of any one of a number of different computer products andmay include aspects of the computer architecture illustrated in FIG. 2,where appropriate. For example, the client systems 104, 106 and 130, 132can include a network interface that enables communication with othercomputing devices such as the server system 102 via the network 108.Wired or wireless network connections may be used with any suitablecommunication protocol, such as TCP/IP. In general, the client systems104, 106, 130, and 132 typically include a processor, a display, and amemory that stores program code and data for operating the clientsystems. The memory of the client systems 104, 106, 130, and 132 mayalso store an application for browsing Web pages, such as the Web pagesshown in FIGS. 9-13.

Exemplary Client System

FIG. 3 illustrates one exemplary client system in the form of an eBookreader device 300. However, virtually any other type of display devicemay be used. In the illustrated implementation, the device 300 isembodied as a handheld eBook reader device. Various features of thedevice 300 are described briefly below. However, a fuller description ofthis exemplary display device may be found in U.S. patent applicationSer. No. 11/277,893, filed Mar. 29, 2006, and entitled “HandheldElectronic Book Reader Device Having Dual Displays,” which isincorporated herein by reference. For instance, the eBook reader device300 may include a display for rendering content that is implementedusing electronic paper display technology. In general, an electronicpaper display is one that has a high resolution (150 dpi or better) andis bi-stable, meaning that it is capable of holding text or otherrendered images even when very little or no power is supplied to thedisplay. The electronic paper display technology may also exhibit highcontrast substantially equal to that of print on paper. Some exampleelectronic paper displays that may be used with the implementationsdescribed herein include bi-stable LCDs, MEMS, cholesteric, pigmentedelectrophoretic, and others. One example electronic paper display thatmay be used is an E Ink-brand display.

As shown in FIG. 3, the eBook reader device 300 has a body or housing302, a keyboard 304, and a dual display system comprised of a firstdisplay 306 and a second display 308. The device keyboard 304 includes aplurality of alphabetic, numeric, and/or function keys for entry of userinput.

The first display 306 in the dual display system presents content in ahuman-readable format to the user. The content presented in the firstdisplay 306 may be digital works, such as electronic books, newspapers,or other readable or viewable materials. For example, the display 306provides the text of the electronic books and also depicts anyillustrations, tables, or graphic elements that might be contained inthe electronic books.

The second display 308 of the dual display system is a narrow screenlocated adjacent to the content display 306. The narrow display 308 isillustrated as being positioned to the right of the content display 306,although it may be located elsewhere in the housing 302 in otherimplementations. The narrow display screen 308 may be responsive to userinput registered via, for example, a finger, a stylus, or other similarpointing device. Additionally, the narrow display screen 308 may enablepresentation of graphic elements that correspond to content displayed inthe content display 306.

The eBook reader device 300 may also include a variety of user inputs310 to navigate through and among eBooks and digital works. Examples ofuser inputs that may be present include buttons, scroll wheels, thumbwheels, thumb sticks, sensors that detect and register movement of auser's thumb or finger, tactile sensors, or any other conventional userinput mechanism.

The eBook reader device 300 also has various internal components, whichare referred to generally as eBook reader subsystems 312. In oneimplementation, the subsystems 312 include system storage 314 and aprocessing unit 316. The processing unit 316 interacts with the systemstorage 314 to facilitate operation of the eBook reader device 300. Thesystem storage 314 may be used to store one or more eBooks 318,annotations 320, authentication certificates 322, and other content, aswell as software programs or other executable modules 324 that may beexecuted by the processing unit 316. Examples of such programs ormodules might include indexing modules indexing eBooks with invariantlocation reference identifiers, reader programs, control modules (e.g.,power management), network connection software, operating models,display drivers, sensor algorithms, page turn detectors, and the like.

The system storage 314 may include volatile memory (such as RAM),nonvolatile memory, removable memory, and/or non-removable memory,implemented in any method or technology for storage of information, suchas computer-readable instructions, data structures, program modules, orother data. Also, the processing unit 316 may include onboard memory inaddition to or instead of the system storage 314. Some examples ofstorage media that may be included in the system storage 314 and/orprocessing unit 316 include, but are not limited to, RAM, ROM, EEPROM,flash memory or other memory technology, CD-ROM, digital versatile disks(DVD) or other optical storage, magnetic cassettes, magnetic tape,magnetic disk storage or other magnetic storage devices, or any othermedium which can be used to store the desired information and which canbe accessed by the eBook reader device 300. Any such computer storagemedia may be part of the eBook reader device 300.

Various instructions, methods and techniques described herein may beconsidered in the general context of computer-executable instructions,such as program modules, executed by one or more computers or otherdevices. Generally, program modules include routines, programs, objects,components, data structures, etc. for performing particular tasks orimplementing particular abstract data types. These program modules andthe like may be executed as native code or may be downloaded andexecuted, such as in a virtual machine or other just-in-time compilationexecution environment. Typically, the functionality of the programmodules may be combined or distributed as desired in variousimplementations. An implementation of these modules and techniques maybe stored on or transmitted across some form of computer-readable media.

The above-described server systems and client computer systems may storesoftware instructions that, when executed, implement aspects andfeatures of the present invention. For example, such software can bestored on a computer-accessible medium (e.g., magnetic or optical diskor other device), or downloaded from a remote source, for loading intomemory 204 of the server system 102 to be executed by the processor 202,and/or for loading into system storage 314 of the client 300 to beexecuted by the processing unit 316. For illustrative purposes,described herein are implementations that allow authors and users toaccess digital works, to annotate digital works, to receive annotationsof those digital works from authors, and to provide annotations ofdigital works to users, possibly in exchange for some form ofcompensation or completed action by the user. Although the illustrativeexamples described herein depict a Web-based implementation, those ofordinary skill in the art will appreciate that other implementations ofthe invention may use other implementations for communication anddisplay of information to authors and users.

Overview of Invariant Location Referencing

As mentioned above, a problem arises when attempting to identify andcommunicate a page or position within a digital work, due to thevariable screen size, font type or size, margins, line spacing,resolution, and other variable display conditions of the displaydevices. This problem applies equally to the communication ofannotations between display devices having varying display conditions.FIG. 4 illustrates the problems arising from variable display conditionsof display devices. FIG. 4 shows two display devices displaying aportion of a Romeo and Juliet eBook. One display device is anineteen-inch computer monitor 400 displaying the eBook in twelve pointfont. The second display device is a PDA 402 with a two-inch bythree-inch screen, displaying the eBook in eight point font. As shown inFIG. 4, both display devices 400 and 402 are displaying content from thesame location in the eBook. However, the computer monitor 400 indicatesthat the displayed content can be found on virtual frame or pagetwenty-nine of the eBook, while the PDA 402 indicates that the displayedcontent is on virtual page one hundred eight of the eBook. Thisdifference in page number is due to the different display conditions ofthe two display devices, and makes it difficult for a user of the eBookto refer another user to specific content in the eBook. For example, auser reading Romeo and Juliet on the nineteen inch monitor 400, would beunable to easily tell a user reading Romeo and Juliet on the PDA 402where to go to read Romeo's metaphor: “Juliet is the sun!”

Invariant location referencing makes it possible to meaningfullyidentify and communicate a specific location or segment of content in aneBook, regardless of screen size, font type or size, resolution, orother display conditions of the display device. Generally, this isaccomplished by assigning unique reference identifiers at locationsthroughout the content of a digital work, or to individual segments ofthe digital work. These reference identifiers are not dependent ondisplay conditions of a display device on which the digital work isdisplayed. In that sense, the reference characters are invariant.

FIG. 5 illustrates an exemplary invariant location referencing schemethat remedies the forgoing problems related to variations in displayconditions. As shown in FIG. 5, a Romeo and Juliet eBook is againdisplayed by two display devices 400 and 402 having different displayconditions. However, in this case, rather than displaying a virtual pagenumber, which could change with changes in display conditions, thedisplay devices display an invariant location reference identifier 500corresponding to at least a portion of the displayed content 502 (shownin a text box for clarity). The invariant location reference identifier500 is a unique identifier that corresponds to a specific location orsegment of content 502 in the eBook, which is not affected by changes inscreen size, font type or size, resolution, or other display conditions.Thus, the invariant location reference identifier 500 provides areference to the assigned text 502 regardless of display conditions ofthe display device. This allows users to easily convey a location ofspecific eBook content to other users reading the same eBook on otherdisplay devices and/or under different display conditions. In addition,the invariant location referencing scheme may be applied to annotationsto identify a specific location or section of text to which theannotation applies.

The invariant location reference identifiers may be provided in additionto any dividing indicia in the digital work itself (e.g., page numbers,chapter numbers, book numbers, section numbers, etc.) and any virtual(variable) page numbering, or may be provided instead of such dividingindicia and/or virtual page numbering. Generally, the invariant locationreference identifiers are separate from the digital work, such that thedigital work is unaltered by the location reference identifiers, thoughnot necessarily. The invariant location reference identifiers provide areliable means by which a user can determine a location of content inthe digital work and approximately where the content is relative to thebeginning and end of the digital work. Invariant location referenceidentifiers may also be used as a means of identifying a source of anannotation, quotation, or excerpt from an eBook, or when one eBookreferences a passage from another eBook (e.g., See Shakespeare, “Romeoand Juliet”, location 201).

There are numerous ways of providing invariant location referenceidentifiers in, or in association with, content of a digital work. Inaddition, there are a variety of ways in which digital works may bepartitioned and assigned invariant location reference identifiers. Forexample, each invariant location reference identifier may be assigned toan individual character or word, a group of words, a sentence, aparagraph, a band of text of predetermined size, a unit of data, or someother division of the digital work. Additional details of partitioningdigital works, generating, assigning, and/or storing invariant locationreference identifiers are described in U.S. Provisional Application No.60/882,870, filed Dec. 29, 2006, and entitled “Invariant Referencing inDigital Works,” which is incorporated herein by reference.

Exemplary Annotation Methods

FIG. 6 is flow diagram of one exemplary method 600 for receiving andproviding an annotation of a digital work. The method 600 may, but neednot necessarily, be implemented using the server system 102 and/or oneor more of the client systems 104, 106, 130, and 132 shown in FIGS. 1,2, and 3. In this particular implementation, the method 600 begins atoptional block 602 in which a digital work is obtained from a source,including but not limited to a publisher, a writer, or other originatorof the work. At block 604, the digital work is provided in a manner thatthe digital work is accessible to others. As noted earlier, the serversystem 102 may include a digital works database 124 with media filescontaining all forms of digital content, such as books, photographs,manuals, music, movies, etc. A directory of digital works in the digitalworks database 124 may be provided to the client systems 104, 106, 130,and 132 by the database manager 220 of the server system 102. Filescontaining the digital works may be requested, displayed, played back,or otherwise consumed by the client systems 104, 106, 130, and 132.Delivery of digital works to the client systems 104, 106, 130, and 132may be accomplished in a variety of ways including, but not limited to,downloading the digital files, streaming the digital files from theserver system 102, or providing access to the digital works at acomputer-accessible source (e.g., by providing a URL to the digitalwork). Additionally or alternatively, as discussed above, digital works,annotations, and/or authentication certificates may be transmitted fromone client system directly to another on a peer-to-peer basis, as shownby the arrow between client systems 106 and 132 in FIG. 1.

U.S. patent application Ser. No. 10/669,088, filed Sep. 23, 2003, whichis commonly owned by the assignee of the present invention andincorporated by reference herein, discloses other exemplary systems thatmay be used in connection with the implementations described herein.Such systems may include one or more databases that include digitalworks in multiple representations. One representation of a digital workmay include images of pages of content, while another representation ofthe digital work may include text searchable forms of the content. Thecontent in the page images correlates with the text searchable form ofthe content. The page images may be stored in a page image database,while the searchable text may be stored in a text searchable database.Images of pages of content may be acquired using methods known in theart, such as scanning printed pages, converting electronic text todocument images, retrieving page images from memory, receiving pageimages from others, etc.

For each image of a page of content, a recognition routine, such as anoptical character recognition (OCR), may be performed on the page imageto identify the text, position, and size of each word on the page andprovide a text searchable representation of the page. A “word,” in thiscontext, may encompass any grouping of one or more characters, numbers,or symbols. Moreover, a word may stand alone or be associated with anon-text object, such as a picture or graphic. OCR routines are wellknown in the art of electronic document processing and do not requirefurther discussion herein. The resulting text, position, and sizeinformation obtained from processing text on page images may be storedin the text searchable database.

The text searchable database may be organized as desired, which mayinclude using data structures optimized for full text searching. In onesuitable implementation, each word in the text searchable database hasassociated therewith content identification numbers for digital works(e.g., SKU numbers) and page numbers corresponding to the digital workand the images in the page image database where the particular word isfound. Furthermore, the text searchable database typically includesinformation that identifies the position and size of the text (andpossibly non-text objects associated with the text) as found on eachrespective page image. In one implementation, the position and sizeinformation is recorded as “quads,” which include four numbersrepresenting the X and Y position and the width and height of the textas it appears on a particular page image. All of this information may beencoded in the text searchable database to reduce the storage spacerequired.

As will be described in more detail below, in some implementations anannotation may be received in regard to particular content of a digitalwork. A text searchable database as discussed above can be used toenable an author of an annotation (or other person, entity or device) toindicate particular content in a digital work and associate anannotation with the particular content. As noted, the text searchabledatabase may be constructed to include information that helps identifythe image(s) in the page image database corresponding to the particularcontent. Thus, when an author of an annotation indicates particularcontent in a digital work by selecting text in the text searchabledatabase, the selected text not only identifies the particular contentthat the author is annotating, but also identifies the correspondingpage image(s) in the page image database where the particular content isrepresented. Word position and size information as discussed above maybe helpful in this regard in that it correlates text in the textsearchable database with the location of text as represented in acorresponding page image.

Supposing, for example, the author 136 (FIG. 1) desires to submit acomment on a digital work, provide updated or supplemental material, orotherwise annotate a digital work, the author 136 enters the annotationsinto the client system 132. The author 136 may enter the annotationsinto the client system 132 in a wide variety of formats depending on thesoftware and hardware provided at the client system 132. In one format,for example, the author 136 may operate a keyboard to enter textannotations into the client system 132. In another format, the author136 may enter graphical annotations, such as handwritten notes ordrawings. The graphical annotations may appear in context with regard tothe digital work being annotated, for example, in the margins, adjacentto, or superposed over or near particular content in a display of thedigital work. Handwritten annotations may be particularly suited wherethe client system 132 includes a sensitive screen that readily acceptshandwritten input. In another format, the author 136 may annotate thedigital work by providing an image file containing an image pertainingto the digital work. When the server system 102 receives an annotationof a digital work from an author, such as author 136, the author mayindicate one or more particular locations or content in the digital workto which the annotation pertains (e.g., using pages from the page imagedatabase, invariant location reference identifiers, or both). In someimplementations, the author 136 may be required to sign in or otherwisesubmit an identification before the author is allowed to submitannotations to the server system 102.

As indicated at block 606 in FIG. 6, the server system 102 may receiveannotations of a digital work from an author. In a circumstance whereauthor 136 is providing annotations to the client system 132, the clientsystem 132 communicates the annotations to the server system 102 via thenetwork 108. Annotations received by the server system 102 may be storedin the annotations database 126, in association with the digital work,as indicated at block 608. Storing an annotation in association with adigital work may be accomplished in any suitable manner, includingsimply storing the annotation in the annotations database 126 with anindication of the digital work to which the annotation pertains, and ifapt, the particular content within the work to which the annotationpertains. Typically, the operator of the server system 102 haspreviously secured an agreement with the author concerning any copyrightor other proprietary interest the author may claim in annotationssubmitted to the server system 102.

Implementations of the present invention have a wide applicability ofwhich the following examples are only a small part. The followingexamples give selected contexts for appreciating several advantages ofthe invention. An annotation, for example, may be a critique oralternatively a summary of the digital work. An annotation may be aseparate essay on the same topic presented in the digital work.Annotations may be words, graphs, formulae, files, images, enhancements,etc., provided by the user. For example, a user may wish to annotate atravel book by providing recent images of locations described in thetravel book. For digital works that are audio, such as music files,authors can annotate the music files with additional content commentingon the songs, providing background information on the singer or therecording process, alternative lyrics, technical information as to thecomposition, related musical compositions, etc. In a circumstance wherethe digital work is a cookbook, for example, authors may submitalternative ingredients that enhance a recipe, ingredients that make aspicier dish, ingredient substitutions considered to be lower in fat orcarbohydrates, etc. In another circumstance, a student or teacher as anauthor may provide a markup of an academic textbook. As can beappreciated from the foregoing, there is virtually no limitation to thetype, form and content of annotations that can be added to a digitalwork. By way of illustration, an annotation can also be in the form of alink or address to another page, file, or document available to theserver system or the client system(s).

A user, such as the user 120 shown in FIG. 1, obtaining a digital workfrom the server system 102 may be notified by the server system 102 thatannotations to the digital work are available. If desired, the serversystem 102 may present one or more summaries of the annotations orportions of the annotations to the user 120 for a preview.

As indicated at block 610 in FIG. 6, the server system 102 may receive auser request for an annotation of a digital work. This request typicallyidentifies the digital work and possibly the particular annotationdesired. Depending on implementation, distribution of annotations ofdigital works may be limited to users having an appropriateauthorization credential that, when presented to the server system 102and validated, enables the user to receive the requested annotation.Additional discussion of authorization credentials is provided below. Asindicated at decision block 612, the method 600 determines whether theuser has presented an authorization credential. If not, the method 600terminates at block 614 by denying the user access to the requestedannotation. If an authorization credential has been presented, themethod 600 determines at decision block 616 whether the authorizationcredential is valid. If the authorization credential is not valid, themethod 600 terminates at block 614 by denying the user access to theannotation. Otherwise, the annotation of the digital work is provided tothe user at block 618. Delivery of an annotation to the user may beaccomplished by downloading the annotation, streaming the annotationfrom the server system 102, transmitting the annotation from one clientsystem to another (peer-to-peer), or providing access to the annotationat a network source (e.g., by providing a URL to the annotation),possibly together with and perceptibly associated with some or all ofthe digital work to which the annotation pertains.

Authorization credentials presented by users may take any formappropriate for processing in the server system 102. For example, anauthorization credential may be a token comprised of symbols or analphanumeric code that is recognized in the server system 102. Users mayobtain authorization credentials for accessing annotations in variousways. For example, a user purchasing a digital work may automaticallyreceive an authorization credential to receive present and/or futureannotations of the digital work without charge. Alternatively, a usermay provide some form of compensation to the server system 102, such asa monetary payment or other item or representation of value. A user mayalso receive an authorization credential as an incentive for performingan action specified by the server system 102. For example, a user mayreceive an authorization credential for electronically previewing adigital work or purchasing one or more related digital works orannotations. Users may also receive authorization credentials forperforming actions such as filling out surveys, participating in games,or providing annotations to digital works. In some circumstances, freeaccess to annotations may be provided by simply giving the user anauthorized credential when the user requests access to the annotation.

The server system 102 is configured to receive an authorizationcredential from a user requesting an annotation and to determine whetherthe credential is valid, thus enabling the user to access theannotation. A user's authorization credential can be determined valid inany suitable manner, including comparing a user-submitted credential toa list of known credentials that have been authorized and distributed tousers. Use of a credential may cause the credential to be removed fromthe list in this example, in cases where the credential is intended fora single use. Validation of an authorization credential may beseparately communicated to the user or simply followed by delivery ofthe requested annotation to the user.

In other implementations, an authorization credential may be generatedand distributed for use with a specific annotation or group ofannotations and as such, may be used only to authorize access to thespecific annotation or group of annotations. Moreover, depending on theformat of the authorization credential, the authorization credential mayitself identify the annotation to which it pertains. In that case (wherethe authorization credential identifies the annotation), implementationsof the invention may be configured to receive the authorizationcredential and automatically consider it as a request for theannotation. A user may thus request an annotation and present theauthorization credential in a single step.

Authorization credentials can be advantageously used to create a marketfor distribution of annotations to others. For example, where a userintends to submit monetary compensation for annotations, the user may begiven a price list for annotations to a digital work. The user can thenselect which annotations the user desires to receive and pay for theannotations. In other implementations, a subscription model may be usedwhere the user pays a monthly or annual fee to have access to certaingroups or all available annotations. Commercially-available paymentprocessing systems may be used by an online marketplace 138 (FIG. 1) toreceive a payment from the user for annotations.

FIG. 7 is a flowchart illustrating another exemplary method 700 ofannotating a digital work. The method 700 is described as beingimplemented using an eBook reader device 300, such as the one shown inFIG. 3. However, it should be understood that the method 700 may beimplemented using any other suitable client device, such as a PC, a PDA,or the like. In this implementation, the method 700 again begins atoptional block 702 in which a digital work is obtained from a source,such as a publisher, a writer, or other originator of the work, and maybe stored in system storage 314 of the eBook reader device 300. At block704, invariant location reference identifiers are obtained for thedigital work. The invariant location reference identifiers may be storedin an index file separate from the digital work, embedded in a data fileof the digital work, or otherwise associated with the digital work.While obtaining the digital work 702 and obtaining the invariantlocation reference identifiers 704 are shown by two separate blocks, insome implementations, the invariant location reference identifiers maybe obtained along with the digital work itself.

At block 706, an annotation of the digital work is received at the eBookreader device 300. The annotation may be received in a variety of ways,including, for example, being input by a user/author via a userinterface of the eBook reader device 300, being downloaded or otherwiseobtained along with the digital work to which the annotationcorresponds, and/or being received directly from another peer clientsystem. Annotations received from input by a user/author may be enteredusing the keyboard 304, one or more of user inputs 310 (e.g., byhighlighting text, etc.), and/or using a stylus or other pointing deviceif one or both of the screens 306, 308 are touch sensitive.

A determination is made at block 708 if the annotation is specific to aportion of the digital work or a location within the digital work. Ifthe annotation is not specific to a portion of the digital work, themethod proceeds to block 712. However, if the annotation is specific toa portion of the digital work (e.g., a passage of the digital work), atblock 710, one or more invariant location reference identifierscorresponding to the specific portion of the digital work may beappended to the annotation. In this way, the annotation can beconsistently associated with the same content of the digital work ondifferent display devices, regardless of display characteristics. Oncethe invariant location reference identifiers are appended, the methodproceeds to block 712.

At block 712, the annotation is stored. The annotations may be storedlocally in system storage 314 of the eBook reader device 300 and/orremotely in a remote data store, such as annotations database 126. Insome instances, the annotation may be stored in local memory of theeBook reader device, and subsequently transmitted to a remote datastore. The annotation may be stored in an annotation file separate fromthe digital work, embedded in a data file of the digital work, orotherwise associated with the digital work. As mentioned above, if theannotation corresponds to a specific portion of the digital work or alocation within the digital work, the annotation may include one or moreinvariant location reference identifiers, which may be stored togetherwith the annotation or separately. Annotations received by the serversystem 102 may be stored in the annotations database 126 in associationwith the digital work, as indicated at block 712. Storing an annotationin association with a digital work may be accomplished in any suitablemanner, including simply storing the annotation in the annotationsdatabase 126 with an indication of the digital work to which theannotation pertains, and if apt, invariant location referenceidentifiers corresponding to the particular content within the work towhich the annotation pertains.

In some implementations, at block 714, the annotation may be madeavailable to one or more other computing devices. Annotations may bemade available in a number of ways, including being placed on a remotedata store, such as annotations database 126, being shared directly frommemory of the eBook reader 300 or other client system, or the like. Theannotations may be made freely available, or access may require a validauthorization credential as in method 600 above.

Also in some implementations, at block 716, annotations, digital works,authorization credentials, and other content stored locally on the eBookreader device or other client system may be synchronized with a remotecomputing device, and vice versa. Remote computing devices with whichclient systems may be synchronized include remote servers, such asserver system 102, personal computers, other eBook reader devices orclient systems, and the like. By way of example and not limitation, thissynchronization may be scheduled to occur periodically (e.g., everyweek, every other day, every five minutes, etc.), may occur in responseto a change in content on one or more client devices, and/or may occurupon request of the user. One specific advantage of this synchronizationoperation is to allow a user to have access to his or her entire libraryof digital content at each of several client devices. For example, if auser has a PC at home, a laptop at work, and an eBook reader device athis vacation home, each of these client devices may by synchronized witheach other, so that the user has access to all of his or her digitalworks regardless of the location. The synchronization may occur directlybetween client devices (on a peer-to-peer basis) and/or over a networkvia a remote data store. Also, if one of the user's client systemsbecomes lost or stolen, the content will be stored in one or more otherlocations and will, therefore, be retreiveable by the user.

Exemplary Compensation Method

Another aspect of creating a market for annotations of digital works isto provide incentive for users to submit annotations. FIG. 8 illustratesa flow diagram of a method 800 in which monetary compensation is paidfor an annotation and some or all of such compensation is distributed tothe author of the annotation. At block 802, the server system 102receives a payment from a user for an annotation, records thetransaction in the transaction information database 128, and providesthe user an authorization credential to access the annotation.Compensation received from the user may be paid directly to the authorof the annotation, or, as illustrated at block 804 in FIG. 8, some orall of the payment may be stored in a separate account by thetransaction information database 128 for distribution to the author.Distribution of compensation to the author may be conditioned on theuser's satisfaction with the annotation. At block 806, feedbackregarding the annotation is received from the user. If, at decisionblock 808, the user's feedback indicates that the annotation wassatisfactory, some or all of the payment stored at block 804 isdistributed to the author of the annotation. If the annotation was notsatisfactory to the user, the server system 102 may process a refund ofthe payment to the user, as indicated at block 810.

It should be noted that “authors” and “users” can be, and typically are,distinct from the persons, entities, or devices that are the creators,originators, producers, publishers, distributors, or other “sources” ofdigital works to be annotated. To further illustrate distinctionsbetween “authors”, “users”, and “sources”, consider a person A whowrites a book that publisher P publishes in hardbound, paperback, audio(e.g., “books on tape”), and/or digital forms (e.g., electronic booksthat can be viewed using a suitable device incorporating a visualdisplay), these forms of the book being distributed to the public, forexample, through retail outlets such as book stores, book clubs, andonline marketplaces accessible via computer networks. As to the last,publisher P may authorize the limited reproduction of all or selectedportions of the book by such online marketplaces for promotionalpurposes.

Now consider a person B who wishes to write a review of the book, as fora newspaper, magazine, online journal, or even for one of the onlinemarketplaces that offers the book for sale. In accordance with suitableimplementations of the invention, person B's review can be (or canbecome) an annotation to A's book, given proper authorization(s) by A,P, and/or B for this to occur, and can be bought, sold, traded, rented,etc., at the same online marketplace as A's book and/or at other onlinemarketplaces or retail establishments. B's review need not be limited toa conventional self-contained review essay that is written to be readseparately from A's book. Instead (or additionally), in accordance withimplementations of the invention, B may write some or all of the bookreview as a set of annotations that pertain to, and are fullyunderstandable when read in context with, specific sections or passagesof the book.

For example, B's review may focus on textual passages or pictures ordiagrams in A's book that, to B's sensibilities, seem particularlynoteworthy, and link or associate these with corresponding portions ofthe review. In other words, B annotates the passages or images, and theannotations, taken together, make up some or all of B's book review.

With A's original work and B's review now available, it becomes possiblefor another person C to annotate both A's book and B's review thereof,as digital works. A and/or B may, if they choose, respond to C'scomments and to one another, with all these comments and responses beingadded as yet further annotations to A's book, suitably limited to orassociated with pertinent passages and/or prior annotations, asappropriate, that are read in context with the pertinent sections orpassages of the book.

The entire set of annotations or subsets thereof (e.g., only C'sannotations, or only A's responses, or only annotations made at thebehest of publisher P) can be made available with appropriateauthorizations from A, B, C, and P, as may be necessary (or, in someinstances, under the doctrine of fair use or other legal rubric withoutprior authorization) for purchase, rental, exchange, or other use by aconsumer D. Thus, A and P may be considered “sources” in this example;B, C and A (in the role of responding to B's and C's annotations) may beconsidered “authors”; and D may be considered a “user”. Further, aparticular online marketplace M (or other forum in which annotations andannotated digital works according to the invention are made available to“users”) may be considered none of these, although it will beappreciated that in some situations where publisher P owns marketplace Mor vice versa, or where A self-publishes a book through M without theassistance of a conventional publisher P, M may be viewed as a “source”.

Specifics of exemplary annotation, presentation, and compensationmethods 600, 700, and 800 are described above. However, it should beunderstood that certain acts in the methods 600, 700, 800 need not beperformed in the order described, may be modified, combined, and/or maybe omitted entirely, depending on the circumstances. For example, inmethod 700, the acts of making annotations available to other computingdevices (714) and synchronizing content with a remote device (716) maybe omitted. Moreover, acts from one method may be combined with actsfrom another method in a variety of combinations.

Also, any of the acts described above with respect to the methods 600,700, and 800 may be implemented by a processor or other computing devicebased on instructions stored on one or more computer-readable mediaassociated with a preference-based media alert system and/or mediasystem.

Exemplary Presentation of Annotations

As will be described below in reference to FIGS. 9-13, annotations of adigital work may be viewable concurrent with or separate from a displayof the digital work. Annotations may be received in graphical form,including handwriting. Annotations may also include highlighting of textin the digital work. In some circumstances where annotations areassociated with particular content in the digital work, the annotationsmay be presented in a manner such that the annotations are normallyhidden and become viewable only when a user positions a cursor orpointer near the particular content in the digital work. Techniques forrecognizing the position of a cursor or pointer within a digital workdisplayed on a screen are known in the art.

Furthermore, indicators may be included in the digital work to identifyparticular content having annotations. In a textual digital work forexample, the indicators may appear as footnotes, graphical icons,symbols, characters, or other indicia that are located with the text.Where the digital work is an audio work or an audiovisual work, anannotation associated with particular content in the digital work may beidentified by an indicator in a playback control provided for playbackof the digital work. In yet another alternative, a digital work havingannotations pertaining to particular content in the digital work mayprovide a listing of contents for the digital work with indicators inthe listing of contents identifying the location of the annotations.

Turning now to the example given in FIG. 9, a browser program 900 may beused to depict a Web page to a user. In the implementation shown in FIG.9, the Web page includes a display of a digital work 902, herecomprising a manual for a cordless telephone. The digital work 902 shownprovides instructions for installation of a new battery back in atelephone handset. The digital work, in this example, is textual inform.

Displayed with the digital work 902 are indicators 904, 906 indicatingthe presence of annotations to the digital work. The indicators 904, 906may be graphical icons, characters, or symbols that are simply displayedwith the digital work. Alternatively, the indicators 904, 906 mayprovide active links that initiate the display of correspondingannotations when a user activates (e.g., checks or clicks on or hoversover) the indicators 904, 906.

The Web page illustrated in FIG. 9 further includes a section 908 fordisplaying annotations of the digital work 902. In some implementations,the annotations 908 may be displayed in a frame that is separate from aframe in which the digital work 902 is displayed. Activating theindicators 904 and 906 in the display of the digital work may cause theannotations section 908 to appear. The particular annotation associatedwith the indicator 904, 906 that the user has activated may appearhighlighted, if desired. Annotations may also be associated with theindicators 904, 906 by use of a suitable numbering system where numbersin the indicators 904, 906 correspond to numbers (not shown) associatedwith each of the annotations.

FIG. 10 is a pictorial diagram of a Web browser 1000 providing anotherexemplary Web page formed in accordance with an implementation of thepresent invention. In this implementation, textual annotations arepresented, but in a separate annotations window 1008 that may appearsuperposed on the display of the digital work 1002. This implementationis particularly suited to environments where the user may activateindicators 1004 and 1006 to cause the annotations window 1008 to appear.Typically, the annotations window 1008 provides a way for the user toclose the window so the user may continue to read the text of thedigital work 1002, if any, hidden behind the annotations window 1008.Standard windowing technology may also be used to permit the user toresize or move the annotations window 1008 within the display of the Webbrowser 1000.

In yet another implementation of the invention, a Web browser 1100, asshown in FIG. 11, may provide a Web page display of a digital work 1102in which annotations 1104 and 1106 are presented in a graphical,handwritten format. The handwritten annotations 1104 and 1106 may bedisplayed just as they are received from the author of the annotations.Of course, such annotations can include graphical drawings as well ashandwriting. An annotation may also be provided in the form of a coloror bold highlight 1108 that is displayed with the text of the digitalwork 1102. As shown in FIG. 11, the annotations 1104, 1106, and 1108 maybe configured to appear to a user superposed on an image of the digitalwork.

Digital works and/or annotations may also be received from authors andpresented to users in an audio or audiovisual form, as illustrated inFIG. 12. FIG. 12 depicts a Web browser 1200 with a Web page thatincludes a playback control 1202. The playback control 1202 provides agraphical depiction of an audio or audiovisual file and typicallyrepresents the duration of the audio or audiovisual file. Additionalplayback controls 1204 may be provided to control the playback of thefile. Where the digital work is an audiovisual work, the visual portionof the digital work may be displayed in a section 1206 of the Web page.

Annotations to the audio or audiovisual work may be indicated byindicators 1208 and 1210, for example, associated with the playbackcontrol 1202. In the implementation shown in FIG. 12, the annotations1208 and 1210 are associated with particular content in the digitalwork. For instance, where the digital work is an audio recording of theinstallation manual shown in FIGS. 9-11, the annotations may beassociated with particular steps in the installation as they occur inthe audio recording. Activating the indicator 1208, for example, maycause a window 1212 to appear with a textual annotation associated withthe particular installation step being described in the audio playback.

Alternatively, a digital work may be presented in textual form withannotations in an audio or audiovisual format. Activating an indicatorin the display of the digital work may cause a playback control 1202 andcontrols 1204 to appear for operating the playback of the annotation tothe digital work. If the annotation of a digital work is an image,activating the annotation indicator in the digital work may cause awindow, such as window 1206, to appear with the image annotation. Asshould be appreciated from the foregoing, the presentation and format ofannotations of digital works is not limited.

FIG. 13 illustrates yet another implementation of the present inventionin which multiple annotations for the same content in a digital work arepresented to the user in a form of a list. The Web browser 160 in FIG.13 is shown displaying a Web page with a digital work 1302 in textualform. Indicators 1304 and 1306 in the digital work 1302 indicate thepresence of one or more annotations. Should a user activate theindicator 1304, for example, an annotations window 1308 may appearproviding a list of annotations to the user. The annotations in the listmay be presented to the user in an order determined by reference to acriterion. For example, one criterion may be a ranking of theannotations assigned by others who previously have viewed and “voted” onthe quality of the annotations. Those annotations having a higherranking may be presented first. In circumstances where annotations areprovided to users in exchange for monetary compensation, the users aremore likely to select those annotations previously deemed to be ofhigher quality.

Another criterion for ordering a list of annotations is the priceassigned to each of the annotations. A user may choose to have thelowest priced annotations or the highest priced annotations listedfirst. Yet another criterion for determining the order of annotations isthe date of receipt of each of the annotations. For example, annotationsthat are more recent may be presented above annotations that are older.Other suitable criteria can be readily recognized by persons havingordinary skill in the art.

In some circumstances, user receipt of annotations may be conditioned onprior purchase of the digital work to which the annotations pertain.Conditioning the receipt of annotations on the purchase of theunderlying digital work provides incentive to users to purchase thework. Moreover, authors of underlying digital works are more likely togrant permission to users to add annotations to the digital work, wheresuch permissions are necessary. A user's purchase of the underlyingdigital work may be recorded by the transaction manager 222 in thetransaction information database 128 and later referenced when the userrequests the annotations to the digital work.

Also as noted earlier, authors submitting annotations may indicateparticular content in the digital work to which the annotations pertain.Where the digital work is, for example, a book, annotations may pertainto the whole work or particular portions of the work, for example, achapter, certain pages, or certain text on a page.

Further implementations of the invention may allow users to receiveauthorization credentials to access annotations from one or moreauthorized distributors of credentials. For example, an entity providingonly annotations to digital works may have a relationship with an onlineretailer that permits the online retailer to give authorizationcredentials to purchasers of digital works, which authorizationcredentials are valid for use in accessing annotations of the purchasedworks from the entity. In another circumstance, the author of anannotation may become an authorized distributor and distributeauthorization credentials to others, allowing them to access theparticular author's annotations. Distribution of access credentials inthis manner may be advantageous where an author wishes to provide accessto his or her annotations to selected family, friends, etc. For example,a group of students in a class or book club may each annotate a digitalwork and share their annotations with the others in their group byappropriate distribution of authorization credentials among the group.In yet another environment, a publisher may be an authorized distributorthat distributes valid credentials for accessing annotations to workspublished by the publisher.

In still further implementations of the invention, acomputer-implemented method may be provided which includes obtaining afirst representation of a digital work, the first representationcomprising one or more images. A second representation of the digitalwork is obtained, the second representation comprising content of thedigital work in a form that allows particular content of the digitalwork to be indicated. The particular content is correlatable with one ormore locations in the one or more images at which the content isrepresented. The method further includes receiving an annotation of thedigital work in regard to indicated particular content of the digitalwork, and providing to a user the annotation in context with regard tothe digital work. In regard to the latter, one or more images of thedigital work may be provided to the user such that the annotation isperceptibly associated by the user with the particular content in thedigital work. For example, the annotation may be configured to appear tothe user superposed on one or more of the images of the digital work.Alternatively, the annotation may be configured to appear adjacent toone or more of the images of the digital work. The one or more imagesmay further include an indication of the particular content to which theannotation pertains. The indication of particular content to which theannotation pertains is typically received from the author of theannotation, though it may be received from others.

As previously noted, the annotation may be received from an author thatis different than the source of the digital work. Likewise, the user towhom the annotation is provided may be different than the source of thedigital work. It should be recognized that an annotation of a digitalwork may be further subject to annotation by another author.

In some implementations, the annotation may be provided to the user viaan online marketplace. If desired, the annotation may be provided to theuser together with the digital work via the online marketplace.

While several exemplary implementations of the invention have beenillustrated and described above, it will be appreciated that variouschanges can be made therein without departing from the spirit and scopeof the invention. The scope of the invention, therefore, should bedetermined from the following claims and equivalents thereto.

What is claimed is:
 1. A server system comprising: one or moreprocessors; and one or more computer-readable storage media storingcomputer-executable instructions that, when executed on the one or moreprocessors, cause the one or more processors to perform acts comprising:storing, by the server system, annotation data from a first electronicbook (eBook) reader device to a data store; determining that theannotation data is specific to a digital work; determining that aninvariant location reference identifier is assigned to the annotationdata, wherein the digital work is partitioned into a plurality ofsegments, a first segment has the invariant location referenceidentifier assigned thereto, such that the invariant location referenceidentifier is uniquely assigned with the first segment of the digitalwork, regardless of display conditions used to display the digital work;receiving a request from a second eBook reader device for the annotationdata; synchronizing the annotation data stored in the data store withannotations stored on the second eBook reader device; determining thatthe second eBook reader device has presented a valid authorizationcredential for receiving the annotation data; and sending the secondeBook reader device the annotation data.
 2. The server system of claim1, wherein the annotation data stored by the server system is accessibleby at least a third eBook reader device.
 3. The server system of claim1, the acts further comprising storing, by the server system, thedigital work from the first eBook reader device to the data store. 4.The server system of claim 1, the acts further comprising synchronizingcontent stored on the first eBook reader device with the data store. 5.The server system of claim 4, wherein the synchronization is performedperiodically.
 6. The server system of claim 4, wherein thesynchronization is performed in response to a change in content storedon the first or second eBook reader device.
 7. The server system ofclaim 1, wherein the invariant location reference identifiers areseparate from the digital work, such that the digital work is unalteredby the location reference identifiers.
 8. The server system of claim 1,wherein the location reference identifiers are stored in an index fileseparate from the digital work.
 9. The server system of claim 1, whereinthe location reference identifiers are embedded in a data file of thedigital work.
 10. The server system of claim 1, the acts furthercomprising receiving payment for the annotation data, the payment forcompensating an author of the annotation data.
 11. The server system ofclaim 1, wherein: the receiving of the request for the annotation datais in response to user input received via the second eBook readerdevice; the digital work has been authored by a first author; and theannotation data has been authored by a second, different author.